In many instances in the manufacture of photographic emulsions or dispersions, chemical reactions take place over a very short period of time. Most of these reactions take place in kettles or vessels that are undergoing high shear mixing and that contain high levels of entrained air that result from the mixing operation. In order to understand and monitor the chemistry that is taking place, a means is required to extract and deliver for analysis, bubble free samples.
In the past, liquid samples have been manually or automatically extracted and then delivered to the testing lab for analysis. By the time they were analyzed, the bubbles had risen out of the sample by buoyant forces and therefore bubbles in the sample were not a problem. With the advent of online analyzers and the need for immediate information on the state of the reaction, a method is desired to deliver bubble free samples to an analyzer with minimal time delays, ie, approximately 1 to 2 seconds. One such analyzer is described in patent GB 2071841 A.
Various methods have been described in which ultrasonic waves have been used to eliminate bubbles from process fluids. Methods like those described in U.S. Pat. Nos. 3,904,932; 4,612,018 and 5,022,899 require some sort of holdup volume on which the ultrasonic waves act to either redissolve the bubbles or to push the bubbles away. This is not satisfactory for real time analysis of samples as this operation would be too slow for rapid analysis.
A method for redissolving bubbles inline is described in U.S. Pat. No. 4,205,966. As described in this patent, most of the bubbles are eliminated in the holding kettle as they rise to the surface via buoyant forces. The liquid is extracted from the kettle and pressurized. This pressurization along with the application of ultrasonic waves redissolves the bubbles prior to the liquid being used. This method has the drawback that only a small number of bubbles can be eliminated (less than 1000 per minute in 5 liters or 200 bubbles per liter). However, in many systems the reaction liquids may include up to 30% entrained air and the delivery line is not pressurized. Therefore the method described in this patent would not allow the extraction of bubble-free samples in these situations.
A method for creating a bubble free volume in a bubble laden liquid is described in U.S. Pat. No. 4,825,688. This method has the drawbacks that no sample is extracted from the volume, and that the ultrasonic generating crystal is either immersed in the fluid or mounted through the side of the kettle.
The present invention solves the problems of the devices discussed above. Specifically, the present invention allows one to remove a bubble free sample from a bubble laden liquid. In addition the bubble free sample is available for immediate analysis thereby providing real-time information about the characteristics of the bubble laden liquid.